Prove these identities:
sin([a/4]+b)+sin([a/4]-b)=(√2)cos b
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Maths唔識抵死題(2)
2010-09-16 3:42 am
回答 (2)
2010-09-16 4:34 am
✔ 最佳答案
sin(a / 4 + b) + sin(a / 4 - b)= sin(a / 4)cosb + cos(a / 4)sinb + sin(a / 4)cosb - cos(a / 4)sinb
= 2sin(a / 4)cosb
請問a=兀嗎?
a=兀,
2sin(a / 4)cosb
= 2sin45cosb
= 2(sqrt2 / 2)cosb
= sqrt2cosb
=(√2)cos b
2010-09-16 5:49 am
好在我識呢條，唔駛死
收錄日期: 2021-04-23 21:04:56
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100915000051KK01105